Myopia affects approximately 25% of the population of the United States. Of these, 1%-2% develop pathological myopia--the seventh most frequent cause of legal blindness in the U.S. Pathological myopia results in an elongated eye. Collagens, in conjunction with other components of the extracellular matrix, are a major determinant of the ability of the sclera of the eye to resist stretch. The sclera is made largely of collagen types I and III. Collagen type III is less able to resist stretch than is collagen type I. The amount of collagen type III relative to collagen type I decreases as the eye matures. Tree shrews are mammals, closely related to primates, in which myopia can be experimentally produced by monocular visual deprivation (MVD). Although the appearance of the sclera resembles that seen in human pathological myopia, yet little is known about collagen maturation in the normal sclera of either shrews or humans. Using specific cDNA probes, this pilot project will examine changes in the topographical distribution of expression of collagen type Ia(1), type Ia(2), and type IIIa(1) mRNA transcripts during the maturation of normal tree shrew eyes. Preliminary results demonstrate that probe cDNA, which does for human procollagen type Ia(2), hybridizes with mRNA extracted from cells grown in culture from explants of normal adult tree shrew scleras. This is further confirmed by in situ hybridization (ISH) studies on cultured tree shrew fibroblasts. Specific Aim 1 of this project uses scleral fibroblasts cultured from normal adult tree shrews to test the hybridization of cDNA probes for human procollagen type Ia(1) and human procollagen type IIIa(1) to tree shrew mRNAs. Specific Aim 2 uses in situ hybridization (ISH) and specific cDNA probes to determine the topographical pattern of distribution of cells expressing mRNAs coding for procollagen type I a(1) and a(2), and procollagen type III(a)1, and the changes that occur during maturation of normal tree shrew sclera. Comparisons will be made after the shrews have had 15, 45, and 75 days of visual experience. At 15 days the sensitive period for myopic induction has not yet begun, at 45 days it is at its midpoint, and at 75 days the eye has almost achieved adult dimensions. The results of this project will provide the basis for the study and comparison of the gene expression of extracellular matrix components in the myopic eyes and paired normal control eyes of MVD tree shrews, and in the human sclera during normal aging and during the development of pathological myopia. Target population: Investigators located in largely non-research environment.